Now William Copeland at Duke University in Durham, North Carolina, and his colleagues have shown that it can have lingering physiological effects too. They tracked 1420 9-year-olds right through their teens. Each child was seen up to nine times during the study and quizzed about bullying. The team then measured levels of C-reactive protein in their blood. CRP is a marker of inflammation linked to higher risk of cardiovascular disease and problems like diabetes.

“Because we were collecting biological samples throughout we were able to look at CRP levels in subjects prior to their bullying involvement,” says Copeland. “This really gives us an idea of the changes bullying brings about.”

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Although CRP levels naturally rise in everyone during adolescence, levels were highest in children who reported being tormented by bullies. Even at the ages of 19 and 21, children who had once been bullied had CRP levels about 1.4 times higher than peers who were neither perpetrators nor victims. In a cruel twist, the bullies had the lowest levels of all, suggesting they didn’t suffer the same health risks. They may even see a benefit from their behaviour, though Copeland stresses it doesn’t vindicate their actions. “The goal would instead be to find other ways to produce this protective effect without it being at someone else’s expense,” he says.

Andrea Danese at King’s College London has previously shown that maltreatment during childhood can lead to high levels of inflammation in adult life. “This new study is a helpful addition in showing that these effects extend to another important childhood stressor,” he says. He suggests that care workers could monitor levels of CRP in children having psychotherapy to see if it is helping to soothe the stress of being bullied.